A semiconductor device may include dummy bumps that are originally unnecessary for circuit operations, in addition to active bumps that achieve electrical connections with external devices for receiving and transmitting power supply voltages and signals.
In the following, a liquid crystal driver including dummy bumps is discussed as one example of such a semiconductor device.
A liquid crystal driver is often mounted on a glass substrate of a display panel. In one known structure for mounting a liquid crystal driver on a display panel, active bumps disposed on the liquid crystal driver are pressed against electrode pads disposed on a glass substrate across an ACF (anisotropic conductive film) to provide electrical connections between the active bumps and the electrode pads.
In a mounting technique using an ACF, it is desirable that bumps are substantially evenly arranged over the surface of the semiconductor device. Accordingly, dummy bumps that have a similar shape to the active bumps may be arranged in a region of the surface of the semiconductor device where the active bumps are not arranged.
Although such dummy bumps are unnecessary for circuit operations of the semiconductor device, protection elements are connected with the dummy bumps as is the case with the active bumps, due to the necessity of electrostatic discharge protection. Interconnections that provide electrical connections between the dummy bumps and the protection elements are further disposed as top metal layers which are closest to the surface of the semiconductor device.
Undesirably, significant portion of the surface of the semiconductor device is occupied by top metal interconnections that connect the dummy bumps with the protection elements. The top metal interconnections which are closest to the surface of the semiconductor device can have a reduced impedance, since the top metal interconnections are allowed to have an increased thickness and width, compared with those disposed inside of the semiconductor device. Accordingly, the top metal interconnections are suitable for use as interconnections of a power supply system.
Especially, an interconnection which supplies a power supply voltage to a module integrated in an internal region of the semiconductor device just below a dummy bump is desirably formed as a top metal interconnection.
Japanese Patent Application Publication No. 2007-103848 A discloses a semiconductor device related to the above-described background. The semiconductor device disclosed in this patent document includes a semiconductor chip. The semiconductor chip includes a pad, a dielectric film and a bump electrode. The pad is formed on a semiconductor substrate. The dielectric film has an opening which exposes the top face of the pad. The bump electrode is formed to cover the dielectric film, including the opening. The size of the pad is smaller than the bump electrode. An interconnection other than the pad is formed below the bump electrode across the dielectric film.